Excitonic effects on the two-photon transition rate in quantum wells

Abstract

We calculate two-photon transition rates of exciton states in GaAs quantum wells for varying well widths. The excitons states are described in the effective-mass approximation and are obtained variationally assuming wavefunctions which are separable in the r-coordinates. The two-photon transition rate is calculated taking explicity into account the sum over all the intermediate states, using a variational procedure. We calculate transition rates of excitons of s-symmetry as well as of p-symmetry which are allowed for polarization of the radiation beam along the growth axis and in the layer planes respectively. From our calculations we find that transitions to s-type excitons have significant rates and we expect them to give rise to well-distinguishable peaks in the absorption spectrum. On the other hand, p-type excitons have small rates and their effect in the absorption spectrum is limited to a small feature at the onset of absorption. These results are in agreement with experiment.